1973 Roadrunner rear mount build?

[73runner4spd]

Hey guys, I currently have two cars, one is my 73 roadrunner that has a factory bottom end 400 engine. It has iron 915 casting heads and .284 .484 purple cam. It goes alright but it is nothing like id like it to be. With that being said I am also building a naturally aspirate 383 lt1 for my 97 z28. I was tossing up the idea of building a stout 400 or 383 big block in the roadrunner and will within the next few years. However due to the naturally low compression of the 400 deck motor I was tossing up the idea of a rear mount turbo. It has the factory forged crank (it is a hipo 400 with a manual behind it) the stock rods and the stock pistons. I know I cannot run too much boost, however I was told by a gentleman at sts turbo that I could safely get away with 5 to 7 lbs of boost as long as I have an electronic boost controller. With that said he said I should see gains of between 100 to 120 rwhp. Like I said I do plan on building another lowdeck motor for this car with around the same compression, with an all forged rotating assembly so I can run more boost. My question is, what type of turbo(s) should I get. I am pretty confident in my fabricating skills to make this work with either a single turbo or twin.

For a twin set up I would eliminate bother of my mufflers and place the turbos where they were. Replace my current 2.5 inch echaust with stainless 3 inch up to the turbos and keep a 3 inch return pipe to my carburetor. Since it is a rear mount with little boost would I need an intercooler? and what size turbos would you recommend for this? Thank you and sorry for the long thread lol

[Kryp2nitE]

http://www.theturboforums.com/forums...rbo-Tech-Forum

That will probably be a better forum to browse through. With a rear mount system you can risk oil starvation and with the amount of real estate available under the hood of the road runner you should really reconsider moving them to the front of the car.

What RPM do you plan on spinning the engine up to?

[73runner4spd]

I figured it would be easier to do than fabbing up some headers. I would get a deep sump pan if I did the turbos. it pulls hard passed 5500 but I try to keep it less than 6200

[turbovanman²]

Nothing wrong with a rear mount setup, but I don't think you need 2 turbos. Not sure on sizing, STS would be able to help there. IC for 5-7 psi won't be needed as the long real estate up front will cool off the air charge.

I am doing a mid mount on my diesel van hopefully in the next few weeks.

[73runner4spd]

Do you think the He351 turbo would work well in this application? do you think I would see a decent gain with only 5 to 7 #s of boost? This is just going to be my street car as Im aiming for 10s na with my chebby and 9s on the giggly juice.

[turbovanman²]

Do you think the He351 turbo would work well in this application? do you think I would see a decent gain with only 5 to 7 #s of boost? This is just going to be my street car as Im aiming for 10s na with my chebby and 9s on the giggly juice.

I would say too small for a single application, as they max out around 500 hp on 4 cyl and the Cummin's, but 2 of them would work.

If you check out Hot Rod and Carcraft, they have some good turbo builds using "normal" engines that crank out 700-1000 hp using a single turbo.

[ShadowFromHell]

If you have room under the hood thats always going to be the BEST place to put them. The rear mounts came to be originally for cars that just didnt have the room under the hood, at least without alot of cutting and removing items like A/C and PS. If you really thing about it, building some manifolds would probably be easier then running new exhaust to the rear, a charge pipe back to the front, a pressure oil line, a pump and return oil line.... And probably even more things I am forgetting about. You could also build a setup like the Buick GN's and run one factory manifold and one custom manifold and a single turbo. Are you thinking carb or EFI? While old school, a suck through system would be easy to setup and probably give the power you are looking for. Ive seen a few pics of suck through setups for big block mopar motor homes. They are rare, but they do exist and may be perfect for you.

[Kryp2nitE]

If you have room under the hood thats always going to be the BEST place to put them. The rear mounts came to be originally for cars that just didnt have the room under the hood, at least without alot of cutting and removing items like A/C and PS. If you really thing about it, building some manifolds would probably be easier then running new exhaust to the rear, a charge pipe back to the front, a pressure oil line, a pump and return oil line.... And probably even more things I am forgetting about. You could also build a setup like the Buick GN's and run one factory manifold and one custom manifold and a single turbo. Are you thinking carb or EFI? While old school, a suck through system would be easy to setup and probably give the power you are looking for. Ive seen a few pics of suck through setups for big block mopar motor homes. They are rare, but they do exist and may be perfect for you.

No way that would fit in a roadrunner

[ShadowFromHell]

Why not? Too tall? Im not very familiar with them but a buddy of mine has one and I know they are not a small car. At the very least it looks like a good start to me.

[Kryp2nitE]

Why not? Too tall? Im not very familiar with them but a buddy of mine has one and I know they are not a small car. At the very least it looks like a good start to me.

I agree, it wont be a bolt in, but maybe a good starting point. Under the hood is huge but not motorhome huge =)

[73runner4spd]

Well, I wouldn't be opposed to running a single under the hood, and the b and rb blocks use the same headers unless its TTI. I have a set of hooker long tubes on it right now, so could I potentially remove my passenger side header and replace it with the turbo exhaust manifold off the rv? And the suck through carb? Does the charge pipe just go into a carb spacer? I was going to run a hat and blow through carb set up thanks